1. Field of the Invention
This invention relates to a recoverable, reinforced and vibration-damping plug used for cased wells, which shall be herein referred to as TPR3, which is part of the tooling used in cased wells, such as oil, water and gas wells. Said plug may be used when it is necessary to temporarily or permanently insulate some areas of the well, allowing multiple operations to be performed, specially those related to large scale perforation where explosive-based methods are used. Examples of said methods are high penetration casing perforation, casing perforation using the tubing conveyed perforation system and conventional casing perforation, these being blasting methods that require large quantities of explosive energy which is released in short periods of time. So, the tools necessary to work with said methods must satisfy rigorous mechanical and thermal requirements. The recoverable, reinforced and vibration-damping plug herein described turns out to be an ideal tool to be used with the abovementioned methods due to its mechanical strength, to the special system provided to be fastened to the casing by means of clamps and to the internal energy absorption devices (vibration dampeners).
For high penetration casing perforation, highly powerful explosives are used, so at the moment of trip there is a high, violent pressure increase till said pressure is dispersed in the well through the fluid therein contained at that moment. The pressure reaches a level which is directly proportional to the shots/foot ratio and to the charge power of the explosives used.
In case of drillings using the casing perforation with the tubing conveyed perforation system the purpose is that the gap between the packer and the recoverable plug be as small as possible and that it be tightly joint so as to rise the pressure inside the casing, so that when being drilled, the accumulated energy may enter as much as possible into the pay zone in order to optimize the drainage channel towards the well, thus optimizing the output. Bearing in mind that in the casing perforation with the tubing conveyed perforation system, the explosive discharges between the plug (fixed at a lower portion of the casing to the discharge area) and the packer (fixed at an upper portion of the casing to the discharge area), and due to the confinements of the space between each punching or due to the design of the discharge chamber where the explosive charge is housed, it is relatively small, so at the moment of the explosion a pressure reaching very high levels, even up to 70000 bars, is generated thus creating extreme strength upon the packer (upstream the chamber) and upon the recoverable plug (downstream the chamber). When the casing is drilled, a by-pass below the packer is open and pressure suddenly drops due to the release of the generated pressure.
In such a situation, the “packer”, being a laid tool having an opposing strength defined by the weight of the casing is not shifted from its original position even when it undergoes a heavy jerk. However, the recoverable plug is suddenly pushed downwards and upwards (due to the sudden increase and decrease in pressure), in a short space of time. The shots received are quite sudden and, in general, it shifts within the casing, since the clamps are broken by the explosive strength, thus losing tightness of the packers, while at the same time several permanent damages are caused to the mechanism, in general ruptures and cracks on its metal members. In some instances, even the casing gets damaged. Of Course, such circumstances leave the plug out of service, and so it must be removed from the well ahead of time to be further replaced, without reaching in full the purpose anticipated.
It is for that reason that TPR3 is an ideal tool for the task above described, since it has been specifically designed to endure the critical conditions it undergoes during the casing perforation using the tubing conveyed perforation system and high penetration casing perforation. It has been tested under several working conditions, having obtained excellent results in all cases. Said results show that even when the TPR3 has been developed to be used in casing perforation using the tubing conveyed perforation system and casing perforation with high penetration loads, its features make it suitable to be used without any drawback in other casing perforation methods or to block fluids in certain portions of the casing.
2. Description of the Prior Art
In the art some devices are presently used as a plug tool in wells where conventional casing perforation, high penetration casing perforation and casing perforation using the tubing conveyed perforation system are employed. Said devices are known in art as recoverable plugs. And their main drawbacks are shifting from the original position in the casing after the casing perforation and/or premature ruptures of its members due to the kind of works performed.
In the first place, there is a recoverable plug comprising gripping means with a double set of clamps working over two cones, blocking means with a double set of segments and a pressure equalizer valve with automatic drilling jar and no safety latch.
Secondly, there is a recoverable plug comprising gripping means with a single set of clamps actuated by means of a cone, blocking means with a double set of segments, hydraulic counterbalancing plunger to compensate the shift of the clamps in the casing and pressure equalizing valve with automatic drilling jar and safety latch.
Another variant in the art is a recoverable plug provided with gripping means, one set of double clamps actuating on two opposite cones, blocking means with double set of segments and rotation equalizing valve.
In the fourth place there is another embodiment comprising gripping means having opposite, double set of compression-actuated clamps and an integrated valve inside a mandrel working with “J” shaped latches.
Finally, there is an embodiment of the prior art wherein the plug is provided with a gripping means having a set of double clamps working over two cones, blocking means with a double set of segments and a valve with automatic drilling jar and safety latch.
The TPR3 shows several outstanding features over the prior art which allow to satisfy the needs and overcome any drawback of the existing plugs. The TPR3 includes gripping means provided by a double set of single, opposite clamps having a wall that work over two independent cones, latches with a double set of segments having a reinforced thread and equalizing valve with automatic drilling jar and safety latch. One of the main features of the TPR3 is its shock absorbing capacity, probably due to a shock absorbing device made of highly resistant rubber pieces which are strategically arranged. Said device allows to endure high pressure shots produced by high penetration casing perforation, casing perforation using the tubing conveyed perforation system and conventional casing perforation, avoiding shifting after such operations are made and also early ruptures of its members as a consequence of casing perforation.
Advantages of TPR3 over the five existing recoverable plugs are as follows:
As regards the first embodiment mentioned, the lockout valve of the invention provides the necessary safety so as to no to cause an unwanted release of the plug. The shock absorbing device allows endurance of shots produced by differential pressures caused by high penetration casing perforation, conventional casing perforation and casing perforation using the tubing conveyed perforation system, thus preventing shifting of the plug within the casing after said operations are made. The other plugs, even if they can endure the shots of the casing perforation using the tubing conveyed perforation system without having inner members damaged, they fall through the casing up to 15 meters when the explosive discharge takes place, and such shifting greatly reduces the efficiency of the process due to the expansion of the chamber where the discharge is produced. If there is a water production region below the area where the casing perforation is performed, the plug shifting may lead water flow to be mixed with the fluid obtained in the drilled area.
In some cases, the members of the standard plugs may early break as a consequence of the casing perforation. The lower mandrel and the blocking segments having reinforced thread features a tooling in the parts that are used in the deepest areas in the thread allowing to bear higher pressure and shots without causing early ruptures and providing a higher life to these parts.
As regards the second plug, the safety in latching is mechanically obtained and it is not dependant, as in the case of the hydraulic piston. Besides, it has the advantages provided by said shock absorbing device.
As regards the third embodiment already known, the addition of an automatic equalizing valve with safety latch prevents compulsory shifting to equalize pressures, but there is no assurance as regards the simultaneous release of the clamps. As in the previous comparisons, the addition of the shock absorbing device prevents shifting, as well as the addition of the automatic equalizing valve having a latch.
Reference is made now to the fourth embodiment. This invention ensures that no accidental block is created due to dirtiness in the “J” shaped internal valve, and such dirtiness may be washed with a dredger.
Regarding the fifth embodiment, this invention ensures that the plug shall not shift in the casing as said shock absorbing device is included. Also, because it does not have opposite, single clamps, but clamps which are supported in a completely independent way and a mandrel having a reinforced thread, the fixing to the casing is even more efficient.
In other aspects, it is a tool having three or four packing elements, depending on the configuration, that provide for the highest safety during insulation and that —notwithstanding how deep it is used and the inner diameters of the casing—have interchangeable diameters, compound quality and hardness.
The stroke of the packing allows that, even when two out of its three or three out of its four elements may be lost, the tool retains its insulating capacity.
The grips—comprising two sets of opposite, single clamps having a wall that allows an homogenous rest, with a large contact surface between the clamps and the pipe, thus avoiding that the shots may cause premature ruptures and two sets of independently-moving cones—allow for tightening of the tool to the casing when its own interlocking is required under the need of upwards and downwards motions.
Such set of opposite, single clamps with a wall is present in an attack option based on cement teeth or tungsten inserts which results in the benefit of a positive grip, even when the casing may be extremely hard (case number N-80, P-110, etc., according to part lists issued by the American Petroleum Institute). Thanks to the design of the clamps it may rest in full, including its back part on the casing, thus avoiding early ruptures since it is not designed with parts subject to neither lever motions nor pulling, but they are actuated by homogeneous compression.
Compression continuity in the packings, as well as the attachment of the clamps to the casing over its respective cones, is achieved through mechanical means having a reinforced thread and so, they are independent from the efforts generated by the differential pressures when the tool has been placed in the position of fixing.
The equalization of the by-pass pressure is ensured by an equalizing valve having an automatic sliding jar that shall be undoubtedly open when the plug is dredged, even when fixed and packed, while it will turn to automatically close when the detachment of the dredger takes place, which means that the tool has already been placed in its position.
The same equalizing valve having an automatic sliding jar, should upstream or downstream differential pressures exist, allows that such pressures be equalized before releasing the tool and provides a good degree of safety as regards the work and normalization time of the packing elements which results in a longer live.
The dredging system is an automatic “J” shaped grip and thus, suitable to match the pins of a conventional female dredger that, when entering into the plug while being lowered, opens its sliding valve proving at the surface level that the coupling has been made correctly. Besides, when the dredger is raised, some friction fingers are used to consolidate gripping during the lowering or pulling operations, thus avoiding the accidental loss of the tool and also, keeping the valve open to circulation.
Finally, its shock absorbing device—comprising rubber rings that associate the lower cone of the clamps with the joining sleeve and locking segments—prevents that shots, produced by conventional casing perforation, high penetration casing perforation and casing perforation using the tubing conveyed perforation system, be directly transmitted thorough the tool into the locking segments, damaging the reinforced thread of the lower mandrel which prevents shifting during such operations, and that these impacts be transferred to the casing as well as the early rupture of its pieces as a consequence of casing perforation.